Introduction

The changing scenario in recent times has made computers or visual display units (VDU) part of our routine existence. From a school going child to a corporate almost every one is using VDU either at work or at home. Numerous studies have focused upon the health hazards while working on VDUs. These have been termed as Repetitive Stress Injuries (RSI) and involve the musculoskeletal system not only due to excessive computer work but also due to faulty workstations. It has been found that almost one fourth of patients working on various forms of VDU exhibit visual complaints. It has been found to be proportional to the number of hours working in front of computers., almost 90% of patients complain of visual problems with more than 6 hours of computer work.

Manifestations

The usual symptoms are asthenopia or eyestrain, burning or tender eyes, redness, watering, blurred vision or difficulty in focusing, grittiness or dryness or aching sensation, double vision, feeling of heaviness, headache, tiredness, throbbing and altered color perception. Some patients feel the need to wear prescription glasses and some might require frequent change of spectacles. Systemically some patients might complain of facial rash or dermatitis, photosensitive epilepsy, fatigue, while some might complain of behavioral changes.

The problem

The eye symptoms associated with visual display units has been termed as Computer Vision Syndrome. (CVS). The eye consists of various parts which help in the perception of an object, and information of the same is conveyed to the brain through visual pathways. Eye functions like a dynamic camera and is balanced by its intrinsic and the extrinsic musculature. Cranial pathways coordinate information between the two eyes. CVS may be due to ocular factors, personal factors, workstation factors or environmental factors or a combination of the above.

The cause

Special effort is made by the eye while visualizing a VDU unlike while seeing a printed matter. The object presented to the eye itself is made up of numerous pixels which reflects upon the resolution of the monitor and by itself is not a sharp image and excess effort Asthenopia can also occur with accommodation and convergence anomalies. Hence it is more symptomatic in patients with convergence insufficiency. Since accommodative power decreases with age, appropriate modification in the workstation has to be done for persons above forty years. 
The eye front of the cornea is covered by a thin film of tears (inner mucin layer, central aqueous layer and outer lipid layer.) Blinking which normally is 15 to 20 times per minute helps in maintaining the ocular surface health and washing out the contaminants. Working on VDU is associated with a lowered blink rate and increased incidence of dryness and irritation of the eyes. Personal factors like general ill health, lack of nutritious food (food faddism), use of certain medications (antihistaminics), tendency for migraine, level of stress and variable working schedules all lead to symptomatic CVS

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